1. Field of the Invention
The present invention relates to an IC (Integrated Circuit) package assembly, and particularly to an LGA (Land Grid Array) package assembly having a retention mechanism for mechanically and electrically securing the components of the LGA package assembly to one another.
2. Description of Prior Art
IC packages having leads arranged in a land grid array (LGA) are well known as LGA packages. Connectors for removably mounting an LGA package on a PCB (Printed Circuit Board) are known as LGA sockets. An LGA socket comprises a substantially flat insulative housing defining an array of passageways with electrical contacts received therein corresponding with the array of leads of the LGA package. Each contact has a pair of free ends oppositely projecting beyond external surfaces of the socket housing for respectively engaging with corresponding contact pads on a bottom surface of the LGA package and on a top surface of the PCB. To dissipate the heat generated by an IC chip incorporated in the LGA package, a heat sink is commonly applied.
Different methods are disclosed by the prior art for clamping the LGA package, the LGA socket and the PCB together, thereby establishing an electrical connection between the contacts of the LGA socket and corresponding contact pads of the LGA package and the PCB. U.S. Pat. No. 4,906,194 discloses an LGA package assembly consisting of an upper support plate, an LGA package, an LGA socket, a PCB, an insulator, and a lower support plate. The components of the LGA package assembly are fastened to each other by a plurality of threaded screw members sequentially extending through bores defined in each component, which is laborious and tedious. U.S. Pat. No. 5,847,928 discloses another LGA package assembly consisting of a heat sink, an LGA package, an LGA socket and a PCB. The components are fastened together by a clip disposed on a bottom side of the PCB which has two upwardly extending arms inserted in aligned apertures of the PCB and the heat sink. One problem with this design is that the retention force of the clip for fastening the components of the assembly together is not sufficient enough to prevent physical separation therebetween when the assembly is subject to external shock and vibration. Such a physical separation may result in broken circuits between the LGA package and the PCB, thereby adversely affecting the operation of the LGA package assembly.
Hence, an improved LGA package assembly is desired to overcome the aforesaid disadvantages of the prior art.
Accordingly, one object of the present invention is to provide an LGA package assembly having a retention mechanism for securely connecting components thereof to one another.
Another object of the present invention is to provide a retention mechanism for an LGA package assembly for reliably connecting an LGA package to a PCB.
A further object of the present invention is to provide a retention mechanism for an LGA package assembly which is easy to assemble and disassemble.
In order to achieve the objects set forth, an LGA package assembly in accordance with the present invention comprises a PCB, a socket mounted on the PCB, an LGA package coupled to the socket, a heat sink positioned on the LGA package, and a retention mechanism for mechanically and electrically assembling the above components together. Preferably, a metal support plate may be attached to a bottom surface of the PCB for strengthening the PCB, and an elastomer may be sandwiched between the heat sink and the LGA package and also between the PCB and the support plate.
The retention mechanism consists of a spring clip and a lever. The spring clip has a biasing strip attached to a planar substrate of the heat sink and substantially parallel with the substrate, and a pair of engaging legs on opposite ends of the biasing strip, each engaging leg having an engaging toe horizontally extending from a free end thereof. The lever includes an actuation beam attached to the heat sink and extending in a direction perpendicular to the biasing strip of the spring clip. An arcuate section is formed on the actuation beam and is positioned beneath the biasing strip of the spring clip, whereby the lever is rotatable from a vertical position where the arcuate section is contained in a plane parallel with the biasing strip of the spring clip to a horizontal position where the arcuate section is contained in a plane perpendicular to the biasing strip of the spring clip and engages with the biasing strip of the spring clip.
When the lever is rotated to the horizontal position to engage with the biasing strip of the spring clip, the biasing strip is biased upwardly to cause the engaging toes of the spring clip to abut against the bottom surface of the PCB or the support plate, whereby the heat sink is securely attached to the PCB and whereby a reliable electrical connection is established between oppositely projecting contact portions of contacts of the socket and corresponding contact pads on a bottom surface of the LGA package and on a top surface of the PCB.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.